When proteins useful as pharmaceuticals are produced with the recombinant DNA technique, use of animal cells enables complicated post-translational modification and folding which prokaryotic cells can not perform. Therefore, animal cells are frequently used as host cells for producing recombinant proteins.
Recently, a large number of biopharmaceuticals, such as antibodies and physiologically active proteins, have been developed. Techniques that permit efficient production of recombinant proteins by animal cells lead to cost reduction of biopharmaceuticals and promise their stable supply to patients.
Under these circumstances, a method of protein production with higher production efficiency is desired.
β-alanine, by itself, has pH-buffering action and antioxidant action. Such β-alanine is also a precursor of stronger carnosine (Non-Patent Document 1).
In addition, it has been known that β-alanine functions as a signal peptide, organic osmolyte (Non-Patent Documents 2 and 3), and that it plays a role in maintaining enzyme activity by its chaperone-like activity (Non-Patent Document 4).
On the other hand, it has never been known that an increase in the concentration of β-alanine in cells contributes to the improvement of production of a desired recombinant protein in cultured cells.
As a β-alanine synthetase found in the brain, glutamate decarboxylase (GAD) (EC 4.1.1.15) (Non-Patent Document 5) has been known. GAD is also a decarboxylase having activity for synthesizing hypotaurine or taurine. In general, enzymes known to be used in the synthesis of taurine from a sulfur-containing amino acid such as cysteine (Non-Patent Documents 6 and 7) include cysteine sulfinic acid decarboxylase (CSAD) (EC 4.1.1.29) and cysteine dioxygenase (CDO) (EC 1.13.11.20). However, it has not been known that a large amount of β-alanine is produced if cysteine sulfinic acid decarboxylase is strongly expressed in CHO cells. Further, hamster cysteine sulfinic acid decarboxylase and hamster cysteine dioxygenase have not been known, either.
[Non-Patent Document 1]
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